Cathode-ray character-display tube

ABSTRACT

A cathode-ray character-display tube comprises a mask in the form of a segment of a sphere and including a plurality of character-shaped apertures, a conventional cathode-ray gun and deflection mans for developing and focusing on the mask an electron beam having a cross-sectional area comparable to the area of an individual character aperture, and selector means for positioning the electron beam on a desired character of the mask. Between the selector means and the mask is a decelerator electrode and, following the mask, is an accelerating anode including a forward tubular portion facing the mask with an end in the form of a segment of a sphere and concentric with the mask surface and having a central aperture. The rear portion of the anode is frusto-conical and within this portion are mounted pairs of vertical and horizontal beam trajectory correction plates. The tube includes electrodes for focusing the electron beam after passage through the mask onto the anode aperture. Following the anode is a plate electrode transverse to the axis of the tube and having an axial aperture. The tube includes a fluorescent display screen, means for accelerating and projecting a character beam emerging from the anode aperture onto the screen, and deflection means, specifically vertical and horizontal positioning plates, following the transverse apertured plate and the anode. Preferably, a spherical reticulated scan-expanding electrode, convex with respect to the screens, follows all of the previous electrodes of the tube.

United States Patent Burns 3,681,645 Aug. 1,1972

CATHODE-RAY CHARACTER- DISPLAY TUBE Joseph Burns, Pequannock, NJ.

Falrchild Camera and Inarument Corporation Filed: Sept. 15, 1969 Appl. No.: 857,938

Inventor:

Assignee:

Primary Examiner-Benjamin A. Borchelt Assistant Examiner-N. Moskowitz Attorney-Laurence B. Dodds [57] ABSTRACT A cathode-ray characterdisplay tube comprises a mask in the form of a segment of a sphere and including a plurality of character-shaped apertures. a conventional cathode-ray gun and deflection mans for developing and focusing on the mask an electron beam having a cross-sectional area comparable to the area of an individual character aperture, and selector means for positioning the electron beam on a desired character of the mask. Between the selector means and the mask is a decelerator electrode and, following the mask, is an accelerating anode including a forward tubular portion facing the mask with an end in the form of a segment of a sphere and concentric with the mask surface and having a central aperture. The rear portion of the anode is frusto-conical and within this portion are mounted pairs of vertical and horizontal beam trajectory correction plates. The tube includes electrodes for focusing the electron beam after passage through the mask onto the anode aperture. Following the anode is a plate electrode transverse to the axis of the tube and having an axial aperture. The tube includes a fluorescent display screen, means for accelerating and projecting a character beam emerging from the anode aperture onto the screen, and deflection means, specifically vertical and horizontal positioning plates, following the transverse apertured plate and the anode. Preferably, a spherical reticulated scan-expanding electrode, convex with respect to the screens, follows all of the previous electrodes of the tube.

9 Claims, 2 Drawing Figures ADJUSTABLE 00 44 0c POTENTIAL -26 2| Ila l7 |3 l r-fi' x/ I S 12;: 121515; mm a 26o 1 l l l l l l l l r l 1 357i 5 l 36 5i) 5: i is i5 ADJUSTABLE POTENTIAL ADJUSTABLE DC 42 POTENTIAL cxrnonmmr CHARACTER-DISPLAY TUBE BACKGROUND OF THE INVENTION This invention relates to cathode-ray character-display tubes and particularly to such tubes capable of displaying any of a series of alphanumeric characters carried by a mask upon which the electron beam impinges. Such tubes have come into use particularly as readout devices for electronic data processing equipment.

l-leretofore, there have been devised several types of cathode-ray tubes for displaying alphanumeric characters but, in general, they have involved complex and costly electrode structures and have been of undesirably large dimensions, particularly in the axial direction.

It is an object of the present invention to provide a new and improved cathode-ray character-display tube which includes a simple electrode structure comprising a smaller number of electrodes, which has a significantly shorter axial dimension, which provides improved fidelity and reproduction, and yet provides desired adjustable magnification control of the size of the displayed characters.

SUMMARY OF THE INVENTION In accordance with the invention, a cathode-ray character-display tube comprises a mask in the form of a segment of a sphere and including a plurality of character-shaped apertures, means effective to develop and focus on the mask an electron beam having a crosssectional area comparable to the area of an individual character aperture, and a selector means for positioning the electron beam on a selected character of the mask. The tube further comprises an accelerating anode beyond the mask having an end in the form of a segment of a sphere and concentric with and facing the mask and having a central aperture, means for focusing the electron beam after passage through the mask onto the anode aperture, a fluorescent display screen, means for accelerating and projecting a character beam emerging from the anode aperture onto the display screen, and deflection means following the anode for positioning a selected character beam on the display screen.

For a better understanding of the present invention, together with other and further objects thereof, reference is had to the following description, taken in connection with the accompanying drawing, while its scope will be pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 of the drawing is a cross-sectional view, partially schematic, of a cathode-ray character-display tube embodying the invention; while FIG. 2 is an enlarged perspective view of the character mask of the tube of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing, there is represented a cathode-ray character-display tube comprising an envelope 10, a mask 11 in the form of a segment of a sphere and including a plurality of charactenshaped apertures, usually in the form of a two-dimensional array of characters, as shown in perspective in FIG. 2. The mask 1 1 has an annular forwardly extending sleeve 1 la. The tube includes means eflective to develop and focus on the mask an electron beam having a cross-sectional area comparable to the area of an individual character aperture. This means may be in the form of an electron gun including a cathode 12, a control grid 13, and a focusing and accelerating electrode 14 which is shown in simplified form although it may comprise any well known arrangement of accelerating and fee using electrodes. Beyond the electron gun 12,13,14 is disposed selector means for positioning the electron beam on a selected character of the mask. This means may be in the form of vertical deflection plates 15 and horizontal deflection plates 16, which are shown more or less schematically since they may be of conventional construction. Surrounding the plates 16 is a cup-shaped decelerating electrode 17 having its open end remote from the electron gun closed by a conductive mesh 17a. Beyond the mask 11 is an accelerating anode 18 having a tubular portion facing the mask 1 I with an end in the form of a segment of a sphere and concentric with and facing the mask 11, this end having an axial aperture 18a. The forward portion of the anode 18 is frusto-conical, as shown. Within the frusto-conical portion of anode 18 are disposed pairs of vertical deflection or correction plates 19 and similar horizontal deflection or correction plates 20, shown schematically since they may be of conventional construction.

The cathode-ray character-display tube of the invention further comprises means for focusing the electron beam after passage through the mask onto the anode aperture. This means may be in the form of a focusing and character size control electrode 21 between and overlapping the ends of the mask electrode Ila and the tubular portion of the anode 18. Following the anode I8 is an astigmatic plate 22 extending transversely across the neck of the envelope l0 and including an axial aperture 220 through which the character beam is directed by the deflection correction plates 19, 20. The face of the envelope l0 opposite the electron gun I 2,13,14 is provided with a phosphor display screen 23, preferably with a metallized conductive backing 24. The bulb of the envelope [0 is provided with an internal annular conductive coating 25 which comprises means for accelerating and projecting a character beam emerging from the anode aperture 18a onto the screen 23.

The cathode-ray character-display tube of the invention further comprises deflection means following the anode 18 for positioning a selected character beam on the screen 23. This positioning means may take the form of vertical deflection plates 27 and horizontal deflection plates 28. An interplate shielding plate 26 having a central aperture 260 is disposed between the pairs of plates 27 and 28. Surrounding the horizontal deflection plates 28 is a reticulated or mesh scan-expanding electrode 29, the end of which facing the screen 23 is convex with respect thereto. The electrodes 11-14, inclusive, l7, 18, 21, 12, and 29, the conductive coating 25, and the electrode 26 are brought out to extema] terminals 30-38, inclusive, 41, and 26b, respectively, shown schematically for the sake of clarity.

While the potentials applied to the several electrodes may vary over substantial ranges in accordance with the dimensions and applications of the particular tube,

there follow the electrode potentials applied in the testing of a tube substantially as illustrated and described in one mode of operation:

Mask ll l850 volts Cathode l2 l900 volts Control grid 13 l9$0 +50 volts Focus electrode 14 l300 :l 50 volts Decelerator electrode 17 volts Accelerator anode l8 0 volts Character size control electrode 21 l 850 z l00 volts Astigmatic plate 22 0 1:50 volts Conductive coatin 25 10,000 volts lnterplate shield 2 0 volts Scan-expanding electrode 29 0 to 50 volts The pairs of deflection plates and l6, l9 and 20, and 27 and 28 are given zero volts reference potential and the pairs of deflection plates are connected to suitable adjustable DC potential sources 42, 43, and 44, respectively, from which they receive suitable adjustable control potentials.

It is believed that the operation of the cathode-ray character-display tube of the invention will be apparent from the foregoing description. In brief, an electron beam formed by the electron gun 12,13,14 is passed through the vertical selection plates 15 and horizontal selection plates 16 which are energized from the unidirectional voltage source 42, as shown schematically, to position the beam on any desired character of the mask 1 1. It will be understood that, in practice, the adjustable potentials on the plates 15 and 16 will ordinarily be generated automatically by input equipment. The beam passing through the mask 11 is then directed to cross the tube axis by the radial field produced by electrodes 11, 11a, 21, and 18 and focused onto the aperture 180 of the anode 18. However, the trajectory of the beam will be such that, after it passes through the aperture, it is not an axial beam, due to the offset of a particular character of the mask 11 from the axis. The correction plates 19 and 20, also energized from the source of adjustable unidirectional potential 43 controlled in correspondence with the control of the plates 15 and I6, produce a correcting field to bring the electron beam back to the axis so that it passes through the aperture 220 of plate 22. Thereafter, the beam passes through the vertical positioning plates 27 and the horizontal positioning plates 28, which again are energized from the adjustable unidirectional potential source 44 in correspondence with input display positioning information.

In this way, a selected character of the mask 11 is reproduced on screen 23. At the same time, the spherical scan-expanding electrode 29, in conjunction with the conductive coating 25, produces a diverging electron lens between the electrodes 29 and 25, increasing the scan angle and the sensitivity of the vertical positioning plates 27 and horizontal positioning plates 28.

What is claimed is:

l. A cathode-ray character-display tube comprising:

a mask in the form of a segment of a sphere and including a plurality of character-shaped apertures;

means effective to develop and focus on said mask an electron beam having a cross-sectional area comparable to the area of an individual character apersel tit dr means for positioning said electron beam on a selected character of said mask;

an accelerating anode beyond said mask having an end in the form of a segment of a sphere and concentric with and facing said mask, said end having a central aperture;

means for focusing the electron beam after passage through said mask onto said anode aperture;

a fluorescent display screen;

means for accelerating and projecting a character beam emerging from said anode aperture onto said screen;

and deflection means following said anode for positioning a selected character beam on said screen.

2, A cathode-ray character-display tube in accordance with claim 1 which includes a decelerator electrode positioned between said selector means and said mask.

3. A cathode-ray character-display tube in accordance with claim 1 in which said accelerating anode includes a rearward tubular portion facing said mask and a frusto-conical forward portion.

4. A cathode-ray character-display tube in accordance with claim 1 including means following said anode for correcting the trajectory of said beam to compensate for the off-axis position of a selected character.

5. A cathode-ray character-display tube in accordance with claim 3 in which pairs of vertical and horizontal correction deflection plates are disposed within the frusto-conical portion of said anode to compensate for the off-axis position of a selected character.

6. A cathode-ray character-display tube in accordance with claim 1 which includes a plate following said anode disposed transverse to the axis of the tube and having an axial aperture.

7. A cathode-ray character-display tube in accordance with claim 1 which includes pairs of vertical and horizontal positioning plates following said anode.

8. A cathode-ray character-display tube in accordance with claim 6 which includes pairs of vertical and horizontal positioning plates following said apertured plate.

9. A cathode-ray character-display tube in accordance with claim 1 which includes a spherical reticulated scan-expanding electrode convex with respect to said screen and following said anode.

I l III i 

1. A cathode-ray character-display tube comprising: a mask in the form of a segment of a sphere and including a plurality of character-shaped apertures; means effective to develop and focus on said mask an electron beam having a cross-sectional area comparable to the area of an individual character aperture; selector means for positioning said electron beam on a selected character of said mask; an accelerating anode beyond said mask having an end in the form of a segment of a sphere and concentric with and facing said mask, said end having a cenTral aperture; means for focusing the electron beam after passage through said mask onto said anode aperture; a fluorescent display screen; means for accelerating and projecting a character beam emerging from said anode aperture onto said screen; and deflection means following said anode for positioning a selected character beam on said screen. CM,2Thode-ray character-display tube in accordance with claim 1 which includes a decelerator electrode positioned between said selector means and said mask.
 3. A cathode-ray character-display tube in accordance with claim 1 in which said accelerating anode includes a rearward tubular portion facing said mask and a frusto-conical forward portion.
 4. A cathode-ray character-display tube in accordance with claim 1 including means following said anode for correcting the trajectory of said beam to compensate for the off-axis position of a selected character.
 5. A cathode-ray character-display tube in accordance with claim 3 in which pairs of vertical and horizontal correction deflection plates are disposed within the frusto-conical portion of said anode to compensate for the off-axis position of a selected character.
 6. A cathode-ray character-display tube in accordance with claim 1 which includes a plate following said anode disposed transverse to the axis of the tube and having an axial aperture.
 7. A cathode-ray character-display tube in accordance with claim 1 which includes pairs of vertical and horizontal positioning plates following said anode.
 8. A cathode-ray character-display tube in accordance with claim 6 which includes pairs of vertical and horizontal positioning plates following said apertured plate.
 9. A cathode-ray character-display tube in accordance with claim 1 which includes a spherical reticulated scan-expanding electrode convex with respect to said screen and following said anode. 